Such a surface layer may be constituted by another liquid such as a hydrocarbon spill on a stretch of water, for example, or it may be constituted by floating solid particles such as dust, leaves or foam, for example. Examples of the sheet of liquid include a sheet of water which may or may not be confined such as a dock, a river, a lake or even the sea.
Known skimmers include a surface layer spillway which floats above a skim vat from which the decanted substance is removed. Generally, sealing is provided between the skim vat and both the spillway and the body of liquid in which they are immersed by a bellows or a flexible membrane connecting the two members together while permitting the spillway to move relative to the vat as a function of fluctuations in level inside the vat and in the liquid in which they are immersed.
Such a sealing arrangement has the disadvantage that its size needs to be specially adapted to the sizes of the spillway and the vat. Further, the material from which the seal is made is not necessarily compatible with the chemical aggressiveness of the medium in which it is immersed.
Preferred embodiments of the invention provide a skimmer whose seal is easy to realize using means which are readily adaptable to the size of the vat, and made of material capable of withstanding the aggressiveness of the medium with which it is required to come into contact.